"But there is coming an hour, and now is, when the true worshippers shall do reverence to the Father in spirit and truth" (John 4:23).
Saint Gregory Palamas explains:
"The supreme and revered Father is Father of Truth itself, namely, the Only-begotten Son; and the Holy Spirit has a Spirit of Truth, just as the Logos of Truth. Therefore, those who reverence the Father in spirit and truth and hold to this manner of belief also receive the energies through these. For the apostle says that the Spirit is the One through Whom we pray. And the Only-begotten of God says: 'No one cometh to the Father, except by Me' [Jn. 14:6]. Therefore, those who thus do reverence the supreme Father in spirit and truth are the true worshippers, by conceiving the incorporeal incorporeally. For thus will they truly see Him everywhere in His Spirit and Truth. Since God is spirit, He is incorporeal, but the incorporeal is not situated in place, nor circumscribed by spatial boundaries. Consequently, if someone says that God must be revered in some definite place among those in all the earth and heaven, he does not speak truly, nor does he worship truly. As incorporeal, God is nowhere; as God, He is everywhere...He is boundless...Because He sustains and encompasses the universe, He is in Himself both everywhere and also beyond the universe."
One Hundred and Fifty Chapters, Chaps. 59, 60.
Saint John Chrysostom explains:
"Christ here declares nothing else than His incorporeality. Now the service of what is incorporeal must needs be of the same character, and must be offered by that in us which is incorporeal, that is, the soul and purity of mind ... For both Jews and Samaritans were careless about the soul, but took great pains about the body, cleansing it in diverse ways ... Sacrifice then not sheep and calves, but dedicate thyself to the Lord. Make of thyself a holocaust; this is to offer a living sacrifice. You must worship 'in truth'; as former things were types, such as circumcision, and whole burnt offerings, and victims, and incense, they now no longer exist, but all is 'truth'."
Homily 33, P.G. 59:191.